1. Field of the Invention
This invention relates to the field of radio frequency identification (RFID) tag and label detection systems, and to methods of detecting RFID tags and labels.
2. Description of the Related Art
Radio frequency identification (RFID) tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennas and analog and/or digital electronics, which may include for example communications electronics, data memory, and control logic. For example, RFID tags are used in conjunction with security-locks in cars, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. Nos. 6,107,920, 6,206,292, and 6,262,692, all of which are hereby incorporated by reference in their entireties.
As noted above, RFID devices are generally categorized as labels or tags. RFID labels are RFID devices that are adhesively or otherwise have a surface that is attached directly to objects. RFID tags, in contrast, are secured to objects by other means, for example by use of a plastic fastener, string or other fastening means. Nevertheless, RFID devices are referred to herein somewhat interchangeably as “tags” or “labels.”
RFID devices include active tags and labels, which include a power source, and passive tags and labels, which do not. In the case of passive tags, in order to retrieve the information from the chip, a “base station” or “reader” sends an excitation signal to the RFID tag or label. The excitation signal energizes the tag or label, and the RFID circuitry transmits the stored information back to the reader. The “reader” receives and decodes the information from the RFID tag. In general, RFID tags can retain and transmit enough information to uniquely identify individuals, packages, inventory and the like. RFID tags and labels also can be characterized as to those to which information is written only once (although the information may be read repeatedly), and those to which information may be written during use. For example, RFID devices may store environmental data (that may be detected by an associated sensor), logistical histories, state data, etc.
In activating, reading, and/or detecting RFID devices, radio frequency (RF) fields are generally sent over a relatively long range, that is, over intervening free space. Thus detection of devices is accomplished over a significantly-sized region, and spatial discrimination in reading and detection of devices may be difficult.
One concern that has been raised regarding RFID devices is that their ability to be read over relatively long distances may implicate privacy concerns for people having objects with RFID devices attached thereto or otherwise coupled thereto.
In addition, RFID devices may include commercially-sensitive information that is utilized in channels of commerce in supplying products to an end user. It may be desirable that this information rendered ungatherable or more difficult to gather after the product reaches the end user.
It will be appreciated that concerns about possible tracking or other privacy-related issues, or issues involving undesired dissemination of commercially-sensitive information, may inhibit some users from employing RFID devices. Accordingly, it will be appreciated that it would be desirable for RFID devices to avoid the above problems.